Airborne sound generated outside a building can emanate from either human activities or from mechanical noise and travel through walls, doors, floor, and ceiling assemblies. Considerable attenuation is generally needed to reduce the sound level reaching occupants. Installation of sound-attenuating doors is a part of architectural acoustics noise control.
The sound-attenuating properties of a door are reflected in the difference between the incident sound intensity level imposed on one face of the door and the transmitted sound intensity level emanating from the opposite face. The difference is called the “transmission loss.” This loss is measured in decibels on a logarithmic scale with higher numbers indicating that the structure is more capable of insulting a space from or attenuating outside noise.